1. Field of the Invention
The present invention relates to air compressors and more particularly to an improved integrated oil-less, reciprocating high capacity compressor of the type disclosed in commonly assigned U.S. Pat. No. 4,190,402 granted Feb. 26, 1980.
2. Description of the Prior Art
Heretofore, high capacity compressors were of the reciprocating type which was necessitated in order to achieve the required pressure and air handling capacity. Compressors in the two horse power and higher range had motors connected to the compressor through a belt and pulley drive arrangements usually with a flywheel connected to the pulley shaft to assist in carrying peak loads. As a result of the belt and pulley connection, these devices were objectionably large and a real need existed for smaller size high capacity compressors.
A recent solution to the problem of size reduction was to use an integrated design where the drive unit and pump or compressor are connected in an integral unit on a single shaft. However, practical integral units have been limited to fractional horse power devices because of cooling difficulties and the extreme cyclic motor loading. Thus, the prior art high capacity compressors have all been objectionally large in size.
In the high capacity compressors, oil was used to assist in lubricating, sealing and cooling. Oiled surfaces in the cylinder helped to establish a seal between the piston and cylinder and between the valves and valve plates thereby allowing the development of higher pressures. Cooling was enhanced by the oil in two ways. Firstly, the oil would reduce the friction and thereby substantially reduce the friction generated heat. Secondly, the oil would also tend to carry away heat from the various hot spots in the compressor.
Recently a need has developed for high capacity oil-less compressors. In many compressor applications, oil cannot be tolerated, such as when compressors are used in medical devices, computers, instrumentation and certain processing devices.
Thus, a practical oil-less high capacity compressor of reduced size was not available until the development and commercialization of the compressor disclosed in the aforementioned U.S. Pat. no. 4,190,402. A compressor of this type includes a motor having a flywheel connected directly to a motor shaft which drives two opposed pistons that are simultaneously compressed so that the bearing loads are balanced. A double inlet blower is connected to said shaft and has one inlet for drawing cooling air through a crankcase for cooling the connecting rod bearings. A second inlet draws air through a vent formed in a shroud member. The blower discharges the air from both inlets into the shroud member which then directs the air to the cylinder sleeves and heads for cooling purposes. The cylinder, piston skirts and piston rings are self-lubricated by containing a fluorocarbon thereby substantially reducing the heat generating friction between said members.
While an oil-less compressor of the foregoing type has proven to be eminently successful in sizes of 2 and 3 horsepower a commercial need for higher capacity oil-less compressors has been recognized.